Electronic apparatus involving such items as semiconductor devices have circuit density to the level that the contacting locations, such as the pads on the surface of a semiconductor chip which provide the interface with external circuitry, now must be in more than one row and may be at random locations in a larger attachment area. This in turn results in a large quantity of very small and closely positioned contacting locations that require interconnection to outside or external circuitry and which are not uniformly located with respect to an edge of the attachment area. The sizes involved and volume of production are such that normal manual dexterity can no longer be employed. The structural shapes, the materials, the processes and the conditions of processing must be compatible both to make the fabrication possible within the design constraints and to provide reliability over the life of the device and circuitry package.
In semiconductor technology, the connection between the pad or contact area on the semiconductor chip and the external circuitry is made using an array of conductors on an insulating backing member with very closely spaced inner lead cantilevered members extending into a semi-conductor chip accommodating opening with the inner lead member being bonded to the pad or contact area on the chip and the array expanding outwardly to a more easily connectable spacing. This type of conductor array has become known in the art as the lead frame.
In some electronic wiring, the conductors are mounted on flexible insulating backing with solder reflow and thermocompression bonding type connections to pads or connecting locations on electronic devices being made at locations along the edges of the devices.
Generally, in the art, the contacting area has been confined to a small region in the vicinity of the edge of the device or circuitry being contacted.
As the art has continued to progress, a variation of the lead frame technology has evolved in which a conductor pattern, such as an array of leads, is placed on a dielectric tape filament. One version of this technology is known as flexible tape wiring or FLEX tape. Another version for high precision device contacting is known as Tape Automated Bonding (TAB). It facilitates many registration aspects in automated semiconductor packaging. In the TAB technology, the conductive connecting members extend as beam leads cantilevered into an opening for the semiconductor chip in the tape filament. The TAB technology is described in the "Microelectronics Packaging Handbook" edited by R. R. Tummala and E. J. Rymazewski, published by Van Nostrand, (1989), pages 409-431.
The specifications in the art have now reached the range where multiple rows of pads are being used on the chip to relax spacing constraints as illustrated in Japanese patent 55-12791 and widening the ends of the connecting leads is used in relaxing registration problems as illustrated in Japanese patent 54-124677.
In electronic packaging where lead size and spacing is 5 mils or less on 10 mils or less separation, it is becoming increasingly difficult to achieve high yields of reliable bonded contacts to the packages.